Senki Survival Saga: Isekai no Unmei wo Kaketa Mujintou Fujun Iseikouyuu

Anastasia, an elf said to be the most powerful magical talent in a thousand years, is fighting in the final battle of a three-way war. In the midst of battle with her arch-enemies, the demons, Anastasia finds herself enveloped in an intense light, and wakes up on a deserted island in another world.